A sensor for helium leakage detection and orientation based on a two-dimensional acoustic topological material

Helium, a scarce gas, is widely used in various fields, like aerospace, semiconductor manufacturing, biomedicine, etc. However, the detection of helium leakage remains challenging because helium is an inert gas with exceptional chemical stability, and, thus, traditional gas sensors working with gas absorption cannot be applied in helium sensing. In this work, we create a helium sensor on the basis of an acoustic topological material, which works with the shift of topological corner states and does not rely on chemical absorption. The sensor is created with a two-dimensional Kagome structure, producing corner states at three corners. Theoretical analysis and experimental measurement demonstrate that the sensor possesses a constant relative sensitivity, which is marginally influenced by working conditions. As a result, the sensor can be applied in extremely wide ranges of temperature and humidity and does not require calibration. Furthermore, three corner states arising at distinct positions are adopted to orientate the leakage point. Additionally, because of topological protection, the corner states are marginally influenced by defects in the sensor, and, thus, multiple and large gas input holes are allowed to considerably speed up the response and recovery of the sensor. The sensor exhibits good stability, repeatability, and rapid response without basement shift in helium detection and is available in the detection of various inert gases. Meanwhile, this work provides insights into the application of two-dimensional acoustic topological materials.